package sy.sy6_8;

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in); // int a = 10;
        int n = sc.nextInt();
        Media[] ms  = new Media[n];
        for (int i=0; i<n; i++) {
            String type = sc.next();
            if (type.equals("book")) {
                String name = sc.next();
                double price = sc.nextDouble();
                ms[i] = new Book(name, price);
            }else {
                ms[i] = new DVD(sc.next());
            }
        }
        double rent = MediaShop.calculateRent(ms, sc.nextInt());
        System.out.printf("%.2f", rent);
    }
}

/* 请在这里填写答案 */
abstract class Media {
    public abstract double getDailyRent();
}

class Book extends Media {
    String name;
    double price;

    public Book(String name,double price) {
        this.name = name;
        this.price = price;
    }

    @Override
    public double getDailyRent() {
        return price * 0.01;
    }
}

class DVD extends Media {
    String name;
    public DVD(String name) {
        this.name = name;
    }
    @Override
    public double getDailyRent() {
        return 1;
    }
}

class MediaShop {
    static double calculateRent(Media[] medias, int days) {
        double sum = 0;
        for (int i=0; i<medias.length; i++) {
            Media m = medias[i];
            sum += m.getDailyRent();
        }
        sum = sum * days;
        return sum;
    }
}